Photograph by Daniel Berehulak, The New York Times

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A burial team wearing protective clothing retrieves the body of a suspected Ebola victim from a house in in Monrovia, Liberia, at the end of August. CDC Director Tom Frieden says isolating victims is key to stopping the epidemic.

Photograph by Daniel Berehulak, The New York Times

Ebola Epidemic Could Top a Million Victims If Not Contained, CDC Warns

U.S. officials unveil a computer model that shows infections could increase dramatically.

Ebola could spread to more than a million people over the next four months if immediate, aggressive, and sustained action isn't taken by the world community, U.S. government officials predicted today.

Between 550,000 and 1.4 million people in West Africa would fall ill with Ebola by late January if the infection rate stays the same as it was in August, according to a projection model released by the U.S. Centers for Disease Control and Prevention (CDC).

The virus, which has been raging out of control since March, has infected at least 5,843 people and has killed 2,803, according to the World Health Organization.

The model was released to demonstrate the price of inaction to the world, CDC Director Tom Frieden said in a news conference.

"Every day counts and will make a difference in our ability to control this," he said.

But Frieden stressed that the problem is not hopeless. "A surge now can break the back of the epidemic," he said. "I'm confident the most dire projections will not come to pass."

Since the data used to create the projection was added to the computer model three weeks ago, he said, the situation on the ground has begun to change as U.S. troops and health workers arrive to train and support local health care workers. (See "Doctors and Nurses Risk Everything to Fight Ebola in West Africa.")

Frieden said additional workers from other African countries have already arrived in the region to provide care at Ebola treatment units.

The CDC has 120 people in Guinea, Sierra Leone, and Liberia—the countries hardest hit by the epidemic—as well as in other nations that are at risk. And logistics teams from the U.S. Department of Defense have begun to arrive in West Africa.

"They are bringing in new personnel pretty much every day," Gayle Smith, a special assistant to U.S. President Barack Obama and a senior director of the National Security Council, said at the news conference.

The United Nations and countries including Cuba, South Africa, the United Kingdom, France, Germany, the Netherlands, and several Asian nations have also stepped up their involvement in the fight. But that may not be enough, she said, adding that the United States continues to press other countries to get involved.

"The essential ingredients are both speed and scale," Smith said.

Dr. John Brownstein, who helps runs an online surveillance program for infectious diseases called HealthMap, said he thinks the CDC's projection range is plausible. He said the difference between the high and low numbers stems from varying estimates of how many Ebola victims have not been counted, a topic of hot debate in the field.

Ebola victims often fail to go to the hospital where they are counted and reported to the World Health Organization because they don't trust the medical system, don’t have the time or money to seek care, die before they can get to hospitals or are turned away by overtaxed hospitals, explained Brownstein, an associate professor of pediatrics at Harvard Medical School and Children's Hospital Boston.

Unique Trajectories

Each of the three countries where the outbreak is centered have experienced a unique trajectory for the spread of the contagion and look different in the model, Frieden said.

In Liberia, as of the end of August, people were still lining up outside Ebola treatment units, which were overwhelmed by the influx. Until enough Ebola centers can be established, government forces are setting up temporary facilities in unused schools and other government buildings, he said, where people can bring their sick family members. One caregiver per patient will be provided with protective gear, Frieden said, and food, water, and painkillers will be available to the patient.

Such basic care can double the chance of surviving Ebola, he said.

In Sierra Leone, the Ebola treatment units were full at the end of August, but were not overwhelmed to the same extent as they were in Liberia, Frieden said.

The CDC model is based on data showing that cases of Ebola exploded in both countries through the end of August, with reported cases in Liberia doubling every 15 to 20 days, and those in Sierra Leone doubling every 30 to 40 days.

The model gives two different projections, one based on the number of known cases and one based on the assumption that those figures undercount the outbreak by a factor of 2.5.

According to the model, isolating patients will turn the tide of the epidemic. The outbreak will begin to decrease when about 70 percent of patients are isolated and in treatment, it estimates. Every month that the 70 percent threshold isn't reached will lead to an approximate tripling in the number of daily cases, the model projects.

"Each day we're not effectively isolating people, not only are people dying and potentially infecting others, but the job of turning it around, of stopping the outbreak gets much more difficult," Frieden said.

The epidemic would eventually end under both scenarios.

Projections were not released for Guinea, for which the model cannot predict the outbreak's course because the country's caseload has been so volatile.

Guinea has already beaten back the virus three times since a two-year-old boy contracted it—probably from eating meat from wild animals—last December. But Frieden said the virus keeps being reintroduced into Guinea by people traveling through the forested area where the borders of the three nations intersect.

"The situation in Guinea is very much in the balance," Frieden said, adding that the country will not be safe from the virus until its neighbors have subdued the disease.